The roll crimp would only be used in a revolver. The taper crimp is what you want to use for semi-auto pistols. The semi-auto uses the end of the case for proper spacing in the chamber. The revolver will be using moon clips for proper spacing at the base of the case. When you use a roll crimp you do need a groove in the bullet for the roll to go into.

I do not know of any manufacture of modern .45 ACP dies that does not use a taper crimp. Taper crimp for .45 ACP dies has been the standard for years.

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While it is true that taper crimp is the standard and proper type of crimp for use of .45 ACP cartridges in auto-loading pistols, there ARE roll crimp dies out there.

Apparently, they are mainly intended for loading .45 ACP cartridges that are to be shot in revolvers using "moon clips" or "half-moon clips" (to allow ejection in double action type revolvers), or the .45 Auto Rim (AR) cartridge (which is intended to be shot without requiring the use of those clips in revolvers that were designed for .45 ACP cartridges with clips).

In revolvers, especially rather light ones, the recoil tends to make the bullets pull out of the cases, and that can tie-up the cylinder so that it can't rotate. A roll crimp is what is used to prevent that from happening in most revolver cartridges.

So, with the dual use of the .45 ACP and the existence of its cousin, the .45 AR, there ARE roll crimp dies made for .45 ACP. RCBS makes them, for example, but usually includes taper crimp dies in their die sets marketed as ".45 ACP dies."

So, it is best to CHECK rather than ASSUME when evaluating some dies that are new to you.

Sounds like a copy of "The ABCs of Reloading" is in order. Often a hard copy with pictures in front of you is much better for learning. It's easier to read and see pics of semi-auto head spacing, than understand from forum descriptions...

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the taper crimp is the standard now but the roll crimp has been used to build a bizzillian 45acp loads for 1911s over the years.my set is like 40years old rcbs set that i use works great roll crimping to .470.My dad loaded on these for years before i started using them.i would like a new set more for the carbide size die than the taper crimp die.someday i'll get a new set and test accurracy between taper and roll crimps. my reloads are very good you just dont want to over do it on crimp.i'd be interested to know if someone has done that test and found a difference. gspman

Autoloader handgun ammo dosn't 'need' crimping at all but it does need to have the case flare returned to body diameter so it can chamber reliabily. It can be done with either a roll or taper crimper but taper crimpers are much less touchy about case length to obtain what you need to do.

Since it's been pointed out that roll crimpers do exist for 45 acp loading, now what you have to find is 45 acp BULLETS with a cannelure,(crimp groove), in order to use them!

Using a roll crimper on a bullet WITHOUT a cannelure will result in buckled cases and deformed bullets. Another thing, case length is most times shorter than what it's supposed to be. Trimming to a uniform length would be required in order to get UNIFORM crimps. That means finding the shortest case, trimming all the rest to that length.

As noted, taper crimps are much more tolerant of erratic case length.

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I would NOT suggest using an actual roll crimp (into a bullet cannelure) on a .45 ACP that is intended to be shot in an auto-loader.

To the extend that the case actually headspaces on the case mouth in the auto-loader, the crimp MIGHT get pushed into the chamber throat/leade and not release the bullet at the usual pressure, raising peak pressure substantially when the round is fired.

Many people may follow this post with statements that THEY use roll crimps on the .45 ACP in auto-loaders all the time and never had any problem. And, for several reasons, that CAN be true. Often, the cartridge is loaded to actually headspace with a semi-wadcutter bullet against the lands, or the extractor will hold the case rim well enough to keep the case mouth from contacting the front of the chamber when the firing pin falls. In situations like that, a roll crimp is held away from the constriction of the chamber throat, and there is no effect on pressure. BUT, change how long the cases are (for instance, buy new brass) and then the saving factor may no longer be pressent.

So, on any essentially straight-walled cartridge that is to be used in an auto-loader, it is best to use a taper crimp that leaves the case mouth at the proper diameter for headspacing. If using a roll crimp die, then the idea should be to get the flare out of the case mouth and leave it at the same diameter that you would obtain with the proper taper crimp.

Times change, we are all more cautious now, and you have to be careful about the advice you give to strangers on the internet.

So just take this as a little history, not a recipe.
One of the old time accuracy gunsmiths, Alton Dinan, I think, recommended a hard roll crimp into the front band of a semiwadcutter bullet. The bullet was seated for headspace control by the SWC shoulder against the origin of the rifling, the case mouth did not come into play. He had the machine rest tests to show that gave better accuracy in his guns.

Speer once sold a .45 ACP JHP with a crimp cannelure. They pointed out that the cannelure was shallow enough that you could crimp into it and still have enough case mouth showing for headspace control.

But a taper crimp applied as an extra step is the way to go these days, especially with the various plated and moly coated bullets available.

Some replies said that roll crimps are only for revolvers. Clarification...roll crimps should/can be used only in those revolvers that must be loaded with MOON CLIPS! Revolvers such as the Ruger Blackhawk in .45 Colt/.45ACP have a .45ACP cylinder that uses standard semi-auto (aka 1911 types) headspace technique (expects to headspace on the case mouth) so should use a taper crimp in this revolver.

Back to the original question, up until very recently all Hornady seating dies did a roll crimp. A Hornady tech explained to me a couple of years ago that they couldn't do a taper crimp and have the floating seater sleeve. Now they can and Hornady sells two different .45 seating dies, one that does a taper crimp and one that does a roll crimp.

I don't care because I almost always want to crimp in a separate step anyway. Otherwise, the bullet is still moving downward in the case while the crimp is being applied. Plus it's just easier to adjust one die for seating and another for crimping. Frequently a bullet change doesn't require any crimp change but almost always requires a seating die adjustment.

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